1. Field of the Invention
The present invention relates to a process for removing a metal surface oxide. More particularly, the invention relates to an improvement in or relating to a process for removing a metal surface oxide which comprises contacting a metallic substance to be deterged with a deterging liquid to introduce electrons into the oxide formed on the metal surface and to remove the oxide by dissolution.
2. Prior Art
Oxides adhere to or grow on inner metal surfaces of apparatuses and piping in thermoelectric power plants, nuclear power plants and chemical plants. Particularly, in the nuclear power plants, radioactive ions contained in a cooling water are incorporated in the oxides.
The inventors proposed previously a process for removing oxides formed on the metal surface (surface oxide).
This previous process comprises contacting a metallic substance to be deterged such as an apparatus or piping with a substantially neutral deterging liquid to introduce electrons into a metal surface oxide layer by an external energy as disclosed in the specification of Japanese Patent Laid-Open No. 85980/1982.
To further improve this process, the inventors attempted to employ hydrogen as a chemical species used for introducing the electrons and to introduce the electrons formed by the following reaction: EQU H.sub.2 .fwdarw.2H.sup.+ +2e.sup.-
into a metal surface oxide layer. However, when hydrogen was used alone, the introduction rate of the electrons was insufficient for increasing the dissolution rate of the metal surface oxide significantly.